The field of the invention is duct work used in heating, ventilating and air conditioning systems ("HVAC") and particularly, channels for reducing the size of duct openings.
Fire damper assemblies are employed in duct work for HVAC systems at various locations. The damper assemblies include a sleeve which connects to the duct work, and the size of the sleeve is often larger than the duct work. A "B-channel" is attached to the damper sleeve to reduce its size to that of the duct work to be attached. Such B-channels are constructed from sheet metal which is bent to the desired channel shape and fastened to one wall of the sleeve. Caulking is used on the ends of the B-channel to completely seal off the interior and prevent air leakage.